In radio communication systems, Base Stations (BS) are utilized to provide radio coverage through specified radio channels within certain geographic ranges, and the geographic ranges are called cells. Generally, the BSs are located in the center of the cells. According to the size of coverage range, BSs may be divided into Macro Base Stations (Macro BS), Micro Base Stations (Micro BS), Pico Base Stations (Pico BS) and Femto Base Stations (Femto BS). In addition, in order to expand coverage or capacity, one or more Relay Stations (RS) may be arranged between a mobile station and a BS. For the mobile station, the RS is equivalent to a BS.
According to the supported communication protocols, BSs/RSs may be divided into advanced control stations and legacy control stations, wherein the advanced control stations are Advanced BSs/Advanced RSs (ABS/ARS) supporting new communication protocols, and the legacy control stations are BSs/RSs which can support legacy communication protocols. Similarly, mobile stations further may be divided into Advanced Mobile Stations (AMS) and legacy mobile stations.
IEEE802.16 standard is an air interface standard proposed in allusion to microwave frequency band, including specifications for the physical layer (PHY) and the Media Access Control (MAC) layer. In the IEEE802.16 standard, the IEEE802.16m including a relay structure is the latest standard technique at present, and the IEEE802.16m is based on legacy standards such as the IEEE802.16e and the IEEE802.16j.
The World Interoperability for Microwave Access (WiMAX) is a Broadband Wireless Access Metropolitan Area Network technique based on the IEEE802.16 standard. Based on above description, the advanced control stations (BSs/RSs supporting the IEEE802.16m protocol) can be compatible with and support legacy mobile stations (mobile stations supporting the IEEE802.16e protocol), similarly, advanced mobile stations (mobile stations supporting the IEEE802.16m protocol) further can be accessed to legacy control stations (base stations supporting the IEEE802.16e protocol or relay stations supporting the IEEE802.16j protocol).
When a mobile station moves to another cell from one cell, in order to keep communication, handover is required. In relevant technologies, the handover process may be divided into several sub-processes: 1. acquiring network topology information; 2. preparing to handover and initiating; 3. synchronizing destination station downlink; 4. stopping the connection between the mobile station and the current base station, and entering the new cell. In the above, the process of acquiring network topology information means that the BS broadcasts a message containing neighborhood BS system information periodically, which is called neighborhood broadcast message below. After receiving the neighborhood broadcast message, the mobile station belonged to the BS demodulates the neighborhood broadcast message to acquire the neighborhood BS information, and uses it as a reference of scanning. In the above, the neighborhood BS means one adjacent to the current service BS of the mobile station or one in a neighboring cell.
When a legacy BS transmits the neighborhood broadcast message through the broadcast way, if there are many neighborhood BSs, the neighborhood broadcast message needs to be carried with system information of multiple BSs, as a result, the number of bytes of this message is very large, therefore a method for fragmenting one neighborhood broadcast message into a plurality of fragmentations for transmission is adopted.
Generally, the neighborhood broadcast message will carry one change count, if the count value is changed, it is indicated that the neighborhood broadcast message is updated. If the neighborhood broadcast message is fragmented, it is required that, only after receiving all fragmentations of the neighborhood broadcast message, the mobile station can acquire the updated neighborhood BS system information and perform operations related to handover, such as scanning of the neighborhood BS.